1. Field of Invention
This invention relates to a means for lathe cutting of contact and intraocular lens blanks by use of a new contact lens mold.
2. Description of the Prior Art
U.S. Pat. No. 4,188,353 granted Feb. 12, 1980 to Charles W. Neefe discloses a method of making plastic aspheric lenses by casting a liquid monomer in a container, polymerizing the monomer to form a solid having an aspheric optical surface formed within the container and cutting a second optical surface on the solid lens material with the container supporting the lens material during the cutting and polishing operation. The aspheric surface of the container is formed by clamping the container in a jig and applying pressure until the desired aspheric curve is achieved.
U.S. Pat. No. 4,229,390 granted Oct. 21, 1980 to Charles W. Neefe discloses the use of plastic molds for molding contact lens blanks. The molds also serve as the holding block to facilitate cutting to the required lens thickness. However, measuring before and after the cutting operation is required to determine the thickness of the lens being cut.
U.S. Pat. No. 4,239,712 granted Dec. 16, 1980 to Charles W. Neefe discloses a method for preparing contact lenses with bifocal correction in the front (anterior) surface of the lens. The lenses are prepared from blanks cast in individual molds. The molds serve as the lathe arbor during the cutting process. Again a series of thickness measurements are required.
In the general practice of the art, the mold containing the cast lens blank is mounted into a lathe by the use of a collet. The use of a collet necessitates several measurements in order to insure obtaining a contact lens of the desired thickness. The collet also subjects the mold to stress which in turn results in poor optical quality due to slippage and lack of alignment necessary for preparation of toric and bifocal types of contact lenses.
In my copending patent application Ser. No. 670,162 filed Nov. 9, 1984, there is disclosed a mold for casting contact lens blanks comprising a hollow frustum conical base having attached to the apex thereof a cup-like molding cavity with a positive of the posterior optical surface of a contact lens in the base thereof and at the other end an opening, there being at least one vertical fin on the exterior surface of the conical base, said fin being below the mold cavity. The mold while containing the cast lens blank is inserted into the concentric tapered ring chuck of a lathe and cut into the desired contact lens. Because of the construction of the mold and the lathe it is possible to cut only concentric radii on the anterior lens surface.